Fixing apparatus providing a fixing apparatus capable of suppressing a temperature rise in a non-sheet-passing portion without degrading first print out time

Abstract

A fixing apparatus includes a thermal conductive member that is in contact with a heater and has a thermal conductivity higher than the thermal conductivity of a base material of the heater, and a thermal-resistant member that is disposed between the thermal conductive member and a support member configured to support the heater, a thermal resistance in a thickness direction of the thermal-resistant member being higher than the thermal resistance in the thickness direction of the thermal conductive member.

What is claimed is: 
     
       1. A fixing apparatus for fixing a toner image formed on a recording material to the recording material, the fixing apparatus comprising:
 a rotatable cylindrical film; 
 a heater including a heat generating resistor formed on a substrate, the heater having a first surface in contact with an inner peripheral surface of the film and a second surface disposed on an opposite side of the first surface; 
 a support member configured to support the heater; 
 a pressure member configured to form a nip with the heater through the film to heat the toner image and fix the toner image onto the recording material at the nip; 
 a thermal conductive member having a thermal conductivity higher than the thermal conductivity of the substrate, the thermal conductive member being disposed above the second surface; and 
 a thermal-resistant member disposed between the thermal conductive member and the substrate, a thermal resistance in a thickness direction of the thermal-resistant member being higher than the thermal resistance in the thickness direction of the thermal conductive member, wherein the thermal conductivity in the thickness direction of the thermal-resistant member is less than or equal to 2 [W/mK]. 
 
     
     
       2. The fixing apparatus according to  claim 1 , wherein the thermal conductivity of the thermal-resistant member is lower than the thermal conductivity of the thermal conductive member. 
     
     
       3. The fixing apparatus according to  claim 1 , wherein a heat capacity in a plane direction orthogonal to the thickness direction of the thermal conductive member is greater than the heat capacity in the plane direction orthogonal to the thickness direction of the thermal-resistant member. 
     
     
       4. The fixing apparatus according to  claim 1 , wherein the thermal-resistant member comprises polyimide as a main material. 
     
     
       5. The fixing apparatus according to  claim 1 , wherein the thermal conductivity in the thickness direction of the thermal conductive member is greater than or equal to 80 [W/mK]. 
     
     
       6. The fixing apparatus according to  claim 1 , wherein the thermal conductive member comprises metal as a main material. 
     
     
       7. The fixing apparatus according to  claim 1 , wherein a thermal resistance X in the thickness direction of the thermal-resistant member is greater than 2.0 [K/W] and less than 12.5 [K/W]. 
     
     
       8. The fixing apparatus according to  claim 7 , wherein the following condition is satisfied:
 0.09X+2.85<Y<2.55X+2.6 [log 10 (J/K·m2)], where Y [log 10 (J/K·m2)] represents a logarithm of a heat capacity per unit area on a surface of the thermal conductive member that is in contact with the heater. 
 
     
     
       9. The fixing apparatus according to  claim 5 , wherein the thermal conductive member is made of material at least one of iron, copper, gold, silver, nickel, brass, silicone rubber, and carbon graphite. 
     
     
       10. A fixing apparatus for fixing a toner image formed on a recording material to the recording material, the fixing apparatus comprising:
 a rotatable cylindrical film; 
 a heater including a substrate made of a ceramic material, a heat generating resistor formed on the substrate, and a glass coat layer covering the heat generating resistor, the heater having a first surface which is a surface of the glass coat layer in contact with an inner peripheral surface of the film and a second surface disposed on an opposite side of the first surface; 
 a support member configured to support the heater; 
 a pressure member configured to form a nip with the heater through the film to heat the toner image and fix the toner image onto the recording material at the nip; 
 a thermal conductive member having a thermal conductivity higher than the thermal conductivity of the substrate, the thermal conductive member being disposed above the second surface; and 
 a thermal-resistant member disposed between the thermal conductive member and the substrate, a thermal resistance in a thickness direction of the thermal-resistant member being higher than the thermal resistance in the thickness direction of the thermal conductive member. 
 
     
     
       11. The fixing apparatus according to  claim 10 , wherein the thermal conductivity of the thermal-resistant member is lower than the thermal conductivity of the thermal conductive member. 
     
     
       12. The fixing apparatus according to  claim 10 , wherein a heat capacity in a plane direction orthogonal to the thickness direction of the thermal conductive member is greater than the heat capacity in the plane direction orthogonal to the thickness direction of the thermal-resistant member. 
     
     
       13. The fixing apparatus according to  claim 12 , wherein the thermal-resistant member is made of material at least one of perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). 
     
     
       14. The fixing apparatus according to  claim 10 , wherein the thermal conductivity in the thickness direction of the thermal-resistant member is less than or equal to 2 [W/mK]. 
     
     
       15. The fixing apparatus according to  claim 14 , wherein the thermal-resistant member is made of material at least one of polyimide, perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), as a main material. 
     
     
       16. The fixing apparatus according to  claim 10 , wherein the thermal conductivity in the thickness direction of the thermal conductive member is greater than or equal to 80 [W/mK]. 
     
     
       17. The fixing apparatus according to  claim 16 , wherein the thermal conductive member is made of material at least one of iron, copper, gold, silver, nickel, brass, silicone rubber, and carbon graphite. 
     
     
       18. The fixing apparatus according to  claim 10 , wherein a thermal resistance X in the thickness direction of the thermal-resistant member is greater than 2.0 [K/W] and less than 12.5 [K/W]. 
     
     
       19. The fixing apparatus according to  claim 18 , wherein the following condition is satisfied:
 0.09X+2.85<Y<2.55X+2.6 [log 10 (J/K·m2)], and 
 where Y [log 10 (J/K·m2)] represents a logarithm of a heat capacity per unit area on a surface of the thermal conductive member that is in contact with the heater.